Free, written about a lot so if that's not good enough I suggest www.lostpassword.com
My mom went on vacation, for safety of her computer she unplugged the computer and everything. When she returned home 1.5 wks later her password won't work. She is not very computer savvy so she only has one account. She says she remembers her password and has checked for caps lock errors. I double checked for caps lock mistakes. Now she cant log on to her computer at all. What can I do to help her get back into her computer without a complete reinstall of window, she doesn't want that.